1. Field of the Invention
The present invention broadly relates to breast cancer treatment and, more particularly, is concerned with an adjustable breast bridge used for patients requiring multiple-plane interstitial radioisotope breast implants.
2. Description of the Prior Art
Breast cancer afflicts thousands of women each year in the United States. Complete removal of the breast, or radical mastectomy, has heretofore been the traditional treatment modality for breast cancer in many patients.
However, a newer treatment which entails surgical removal of the malignant tumor mass followed by radiation therapy to the remaining breast tissue has more recently been accepted as an alternative to mastectomy for selected patients. This radiation is usually delivered by combining external beam therapy with interstitial radioisotope implants.
Radioisotope implants are performed by placing a series of hollow nylon tubes through the breast tissue to form an interstitial plane. These tubes are afterloaded with radioisotopes of varying strength which irradiate a volume approximately 0.5 cm above and below the plane. If the involved breast or initial tumor volume is large, a multiple-plane implant is often required to adequately irradiate the tissue at risk for recurrence. Thus, second, third, or even fourth planes of tubes may be necessary.
Maintaining a uniform interplane distance between the planes of tubes is imperative, if an ideal dose distribution is to be obtained from the afterloaded interstitial radioisotope sources, such as iridium-192 (.sup.192 Ir) seeds. One method of determining the location of the additional planes on the surface of the breast has been by using a ruler. Unfortunately, marking parallel lines on the breast is difficult, due to the variable contours peculiar to each breast surface. Measuring the distance from a previously established plane to a proposed new plane with a ruler is not only very time-consuming, it is often inaccurate. As a result, inhomogeneous isodose distributions within the implanted volume subsequently occur.
Pierquin et al (see "Radical Radiation Therapy of Breast Cancer," Int. J. Radiat. Oncol. Biol. Phys., 1980, vol. 6, pp. 17-24) have described a method obviating the problem of inaccuracy associated with using a ruler by custom-drilling holes for tube insertion locations in a pair of perspex plaques for each patient, with interplane and inter-tube distances being determined pre-operatively. This technique allows proper margins above the patient's ribs and below the skin to be chosen, while maintaining uniform interplane distances. However, the technique has the disadvantage of requiring that a new set of plaques be constructed for each patient, or at best that an extensive selection of different plaque sets be available for use on patients with different breast sizes and tumor volumes.
Martinez et al (see "Irradiation With External Beam and Interstitial Radioactive Implant as Primary Treatment for Early Carcinoma of the Breast," Surg. Gynecol. Obstet., 1981, vol. 152, pp. 285-290), on the other hand, have described the use of a fixed-interval breast bridge which allows marking of the breast at fixed 1 cm intervals in a manner similar to the above-described technique of Pierquin et al. While the fixed-interval bridge can be used for many patients, its inability to provide variable interplane distance selections is a severe drawback, as one is unable to optimize the placement of both the most superficial and the deepest planes relative to the skin and ribs, respectively. Likewise, one is unable to optimize the dose-rate to the implanted sources.
Consequently, a need exists for a more versatile device to locate multiple planes on the breast, the use of which is independent of breast size and shape, and, at the same time, simple, accurate and easy to use.